An antenna device is known that radiates two beams in the different directions by using a plurality of common antenna elements arranged in a horizontal direction. Such antenna device is generally referred to as a dual beam antenna (or twin beam antenna).
The dual beam antenna is configured to arrange antenna element groups in multiple stages in the vertical direction, which are provided with a plurality of antenna elements arranged in the horizontal direction. The dual beam antenna is configured to radiate a plurality of beams to the different directions by respectively feeding to adjacent antenna elements in each antenna element group along with a predetermined phase difference and a predetermined power difference.
Also, as the dual beam antenna, a dual beam antenna configured to adjust an electric tilt angle is known. The dual beam antenna configured to adjust the electric tilt angel can adjust a radiating direction of the beam in the vertical direction, i.e., the electric tilt angle by feeding to each antenna element group arranged in the vertical direction along with a predetermined phase difference and a predetermined power difference.
Meanwhile, when the antenna elements are arranged in the horizontal direction in line, as the width of the antenna device decreases, it is a problem that a distance between the antenna elements decreases, coupling between the antenna elements increases, and desired radiating property fails to be obtained.
As a solution to the problem, a method is known that arranges an antenna element in an even number sequence at a position shifted to an upper side or a lower side in the vertical direction from an antenna element in an odd number sequence, and arranges the antenna element in zigzag (see e.g., PTL 1). By arranging the antenna elements in zigzag, isolation in each antenna element can increases, and property degradation caused by coupling between the antenna elements can be prevented.